In regards to a technique for monitoring whether there is an error in a machine or the like, there is a problem that an alarm sounds regardless of an actual error when maintenance on a machine in operation is performed. As to this problem, a technique is known for distinguishing whether the machine or the like is under maintenance. For example, by preparing in advance a file that records whether or not maintenance is being performed on a machine and using that file, it is possible to distinguish between a change of the state in a machine under maintenance and an error occurred in a normal machine. However, in this technique, it is not possible to handle cases such as when update of a file is neglected, or when for some unavoidable reason maintenance starts before the file is updated.
There is also a technique that determines, based on a state of a connection with a maintenance terminal, whether or not a machine is under maintenance. However, this technique can only be applied to a maintenance system that uses a maintenance terminal.
In other words, there is no technique for notifying start or end of maintenance.